Arrangements are known for aligning one component relative to another such as for placing an object on a carrier, e.g., in assembling one electrical or electronic component on another. Examples of such arrangements are shown in the following prior art.
U.S. Pat. No. 4,880,308 (Shirasu), issued Nov. 14, 1989, discloses an aligning system to position a semiconductor wafer relative to a mask, for an exposure operation. Images of marks on the mask are projected onto the wafer lying on a table, movable in X and Y linear directions and theta rotational direction under the control of a mark detecting optical system, to align the wafer marks with the images. The wafer is disposed on the table without reference to any wafer edge engaging positioning structure for locating the wafer in a predetermined fixed relation thereto.
U.S. Pat. No. 4,861,162 (Ina), issued Aug. 29, 1989, discloses an aligning system to position respective chip regions of a semiconductor wafer, held on a chuck lying on a movable stage, for an exposure operation. The wafer is held on the chuck so that marks thereon for each region are in a predetermined relation to marks on the chuck. A mark detecting optical system aligns each region via an optical mark. The wafer is disposed on the chuck without reference to any wafer edge engaging positioning structure for locating the wafer in a predetermined fixed relation thereto.
U.S. Pat. No. 4,980,971 (Bartschat et al.), issued Jan. 1, 1991, discloses an aligning system using two cameras, a machine vision system and a robot arm, movable in X, Y and Z linear directions and theta rotational direction, to place a semiconductor chip on a substrate held on a chuck, to register chip solder bumps with substrate solder bumps. One camera registers with each of a pair of substrate datum points to locate the substrate in one frame of reference, and the other camera registers with each of a pair of chip datum points to locate the chip in another frame of reference. Based thereon, the vision system controls the robot arm to place the substrate on the chuck and then the chip on the substrate to register the pairs of datum points and thus the solder bumps. The substrate is disposed on the chuck without reference to any substrate edge engaging positioning structure for locating the substrate in a predetermined fixed relation thereto.
U.S. Pat. No. 4,755,053 (Levinson et al.), issued Jul. 5, 1988, discloses an aligning system using an optical device, a machine vision system and a tri-axis alignment stage, movable in X and Y linear directions and theta rotational direction, to position a plate on a substrate so that a pair of plate holes coincide with a pair of substrate targets. Using the optical device, the vision system establishes a pair of coordinate axes X and Y for the target centers and a pair of coordinate axes X and Y for the hole centers, performs a transformation of coordinates and computes the X, Y and theta motions of the tri-axis stage required to move the part disposed thereon relative to the other part otherwise disposed, for coinciding the target and hole centers. The vision system uses known algorithms to find the target and hole centers, and obviously to establish the coordinate axes, transform the coordinates and compute the tri-axis stage motions required. The manner of disposing the substrate and plate on the respective supports supporting them for alignment is not disclosed.
U.S. Pat. No. 4,283,845 (Sigel et al.), issued Aug. 18, 1981, discloses a positioning system to lay down two electronic articles in two predetermined article locations on a carrier. The carrier is placed against three first upright rollers defining a first reference system on a reference surface, so as to define three edge contact points on the carrier registering with the rollers and thereby the positional relation thereto of the two article locations. The articles are positioned above three second upright rollers defining a second reference system, identical to the first reference system, on a plate of a positioning machine, so as to register the articles with the article locations of the second reference system. The carrier is then placed against the second rollers on the plate, and the articles are laid thereon at the article locations of the second reference system. No vision system is disclosed nor any detectable marks on the articles or carrier for vision system use to achieve alignment in relation to the rollers of either reference system.
In certain arrangements of the above type, an object such as a semiconductor device (silicon die, chip) is placed in a precise location on a carrier such as a ceramic substrate for bonding thereto. Typically, curable adhesive is predeposited in lines or dots on the carrier top surface, and the object underside is laid on the adhesive in desired relation to the carrier. The assembled unit is placed in a heating zone (oven) for adhesive curing.
The object may have disposed thereon discrete components of very small size, e.g., 5 to 15 microns in width (diameter). For instance, the object may contain a predetermined array of discrete active pixel imaging elements, e.g., photodiodes, of such small size, which are desired to be located at precise positions relative to the carrier when the object is placed on the carrier. This is significant where the assembled object and carrier unit is to be placed on a further support such as an electronic member (fixture) with the discrete components on the object located at desired precise positions relative to the further support. However, the known arrangements are generally incapable of repeatably achieving high precision positioning within a tolerance of less than the width (diameter) of such a small size component.
It is desirable to have a system for placing an object on a carrier with repeatable high precision, particularly within a tolerance of less than the width size of such a discrete component, e.g., within a tolerance of .+-.2 to 3 or 2 to 4 microns.